The man behind the mass shooting in Las Vegas shot and injured a security guard six minutes before carrying out the attack, officials say, in a major change to the timeline of events.

An array of 58 white crosses - one for each slain victim - also was installed last week near the Las Vegas welcome sign as a memorial. Paddock killed 58 people and injured more than 500 before killing himself.

It was not immediately clear why the timeline of the shooting changed a week later and what its effect could be on the investigation.

Officers initially said security guard Jesus Campos distracted Paddock during his deadly attack and was shot in the leg, a minute before police arrived. The suspect, we know that he attempted to shoot at the fuel tanks, we know that he had some personal protection equipment in the room, we know that the vehicle that was found in the parking garage still, contained binary explosives.

"I do not do sun", Paddock said in the 97-page court document, according to CNN.

Paddock also drilled holes and bolted a metal bar to try to prevent the opening of an emergency exit stairwell door near the door of his room.

During the press conference, Lombardo expressed frustration over the speed of the investigation, blaming Paddock's actions by saying he "purposefully hid his actions leading up to the event".

"In coordination with the FBI's Behavioral Analyst Unit, a comprehensive picture is being drawn as to the suspect's mental state and now we do not believe there is one particular event in the suspect's life for us to key in on", Lombardo said.

It is unclear what happened between the moment the guard came to investigate and was wounded and the time Paddock began shooting.

Admitting she now has a "mental and emotional feeling of insanity", McKendry said she has offered free rides to victims' families to help process what happened.

Crawford said she had an emotional breakdown after the massacre, adding that she feels "guilty" for having known Paddock.

Campos was on "random patrol" as a security officer at the hotel when he found the shooter, said Liliana Rodriguez, who identified herself as a coworker of Campos' at Mandalay Bay on a GoFundMe page she set up for him.

"Every piece of information we get is one more piece to the puzzle in this case", Lombardo said.

In response to rumors circulated on social media, Sheriff Lombardo said there is no evidence to suggest a second shooter exists and added that Paddock was not linked to any "ideologies" that could have influenced the massacre.

After questioning Paddock's girlfriend, Marilou Danley, federal agents returned to Paddock's three-bedroom home resting on a cul-de-sac inside a sleepy retirement community in Mesquite, Nevada.

Law enforcement interviews with Paddock's brother Saturday and Sunday were part of an exhaustive search through the 64-year-old's life.

Country star Jason Aldean, who was performing at the festival when the shooting began, appeared last night on Saturday Night Live. "This is all about recovery now", said Clark County Deputy Chief John Steinbeck, who also serves as the county's emergency manager.

"I did notice-a note on the nightstand near-his shooting platform", he said, CBSreports.

People received their belongings in resealable plastic bags and were asked to check them.